1. Field of the Invention
The present invention relates generally to methods and arrangements for installing a pipeline through an earthquake fault zone, whereby damage to the pipeline during an earthquake is minimized. More particularly, the invention relates to a novel method and arrangement utilizing a bed of spherical bodies that acts to partially absorb and disperse earthquake compression and shear waves, thereby enabling the pipeline to survive an earthquake unruptured.
2. Description of the Prior Art
The art of laying pipelines is well known, and pipelines are today installed in various sizes to transport water, oil, natural gas, coal slurries and the like. In the normal pipeline installation process a trench is dug, the pipeline is laid in the trench, and then the open trench is backfilled with the excavated material. Efforts to improve the conventional installation method have been undertaken, such as that shown in U.S. Pat. 3,568,455, wherein vertical standards are installed to hold the pipeline suspended above the bottom of the trench, and a fill material such as gravel or crushed rock is then placed around the pipeline, with excavated material placed above.
When pipelines are installed by conventional or even such improved methods through an earthquake fault zone, and an earthquake occurs, it is common for the pipeline to be ruptured by the shifting of the earth. When this happens disruption of service occurs, and in addition ecological damage can result. The latter result can be especially severe in the instance of a large diameter pipeline running through a relatively isolated area, and carrying a product such as crude oil. In particular, there is concern about such possible ecological damage in Alaska pipeline projects, which can cross several known earthquake faults.
Up to the present there has been inadequate attention paid to the construction of pipelines across earthquake fault zones, and indeed no method or arrangement is known that can satisfactorily accommodate for the occurrence of a major earthquake, and which at the same time is practical in use. The present invention is intended to satisfy the need for such a method and arrangement.